Various kinds of imaging apparatuses that are configured to form images on sheet media are known. Some such apparatuses form images on sheet media in correspondence to an electronic document file, commonly referred to as a print job. Other types of imaging apparatus perform their imaging function in response to optically scanning an image-bearing sheet media. Thus, examples of imaging apparatuses include laser printers, inkjet printers, thermal imaging devices, photocopiers, etc.
Generally, such imaging apparatuses temporarily secure the sheet media in a registered relationship with an imaging engine (i.e., inkjet print head, etc.) during the image forming process so as to achieve the desired image placement on the media. One kind of device used to temporarily secure sheet media is the capacitive mat. Broadly speaking, capacitive mat devices typically include a number of electrically charged conductors, usually arranged as a grid or matrix within a layer of nonconductive material, to support a sheet of media in registered orientation by way of capacitive (i.e., electrostatic) attraction.
One generally undesirable aspect of capacitive mats is the tendency for the layer of nonconductive material to develop a residual electrostatic charge (known as polarization) over the course of operative time. This polarization tends to reduce the efficiency or ‘holding power’ of the capacitive mat with respect to the supported sheet media. Such loss of holding power can lead to movement and/or mis-registration of the sheet media supported by the capacitive mat during operation, resulting in undesirable or unacceptable imaging quality or media jams thereon.
Therefore, it is desirable to provide methods and apparatus for use with capacitive mats that address the polarization problems discussed above.